The present invention relates to a building material mixer having a mixer drum which can be rotationally driven by a mixer drive, with the mixer drum being rotatably supported by the mixer drive at a mixer frame part, in particular a traveling gear frame part, at one of its end face ends and with the mixer drive having a drive part in particular a hydraulic motor, and a drive transmission connected to the mixer drum.
With building material mixers in the form of truck mixers, which are usually used for the supply of premixed concrete to construction sites, large dynamic forces frequently act on the mixer drum, for example when driving over bumpy approach roads so that the frequently heavily loaded mixer drums cause considerable dynamic bearing forces. On the other hand, twists of the traveling gear frame on which the mixer drum is supported arise when driving on uneven ground so that alignment errors of the bearing points result or the bearing point at the frame side twists with respect to the bearing point at the drum side. These twists and dynamic bearing stresses are particularly problematic on the side of the mixer drum which is supported by the mixer drive since such twists or dynamic bearing forces cannot easily be introduced into the transmission of the mixer drive. To be able to compensate or allow the named twists and alignment errors as a result of frame twists, the connection between the mixer drive and the mixer drum is conventionally made in a yielding manner in that a twist-capable connection part is used for the mixer drum fastening. FIG. 3 shows a conventional mixer drive, more precisely its transmission, which is made as a two-stage planetary gear which is driven by a drive motor not shown in any more detail at the input side and drives a drum flange at the output side, said drum flange being shown at the right in FIG. 3 and being rigidly connected to the mixer drum. The transmission housing of the mixer transmission shown in FIG. 3 is rigidly screwed to a bearing block rigidly connected to the traveling gear. Twists of the traveling gear frame supporting the mixer drive with respect to the mixer drum or vice versa can be compensated up to a certain degree by the drum flange designed to be capable of twisting. As FIG. 3 shows, the said drum flange is directly shaped at the output shaft of the mixer transmission, but is made very thin so that it allows twists as a result of tilting movements. In addition, the bearing of the output shaft supporting the drum flange by obliquely positioned tapered roller bearings is made such that the twist stiffness is also kept very limited by it to permit compensation movements.
The permitting of the named twists and their compensation can, however, bring along fatigue problems. In addition, the vibration problems as a result of dynamic loads can only be solved in an unsatisfactory manner by the solutions known up to now. It would also be desirable to achieve compact solutions.